Chrome Version       : 68.0.3409.0
OS Version: OS X 10.13.3
URLs (if applicable) : https://javascript.info/popup-windows#example-a-minimalistic-window

What steps will reproduce the problem?
1. Go to a website that opens a popup e.g. https://javascript.info/popup-windows#example-a-minimalistic-window
2. Open a popup

What is the expected result?
A popup with a top window frame bar should appear.

What happens instead of that?
The top bar is transparent and the page contents are underneath it. See screenshot attached.